Various HIV vaccine strategies have been successful in eliciting virus- specific humoral and cellular immune responses. However, none have proven sufficiently effective in preventing infection with the AIDS viruses. The recombinant pox viruses remain of central importance in these HIV vaccine development efforts. These viruses, constructed to express AIDS virus genes, have been extensively evaluates as priming immunogens for eliciting cytotoxic GT lymphocyte (CTL) responses in non-human primates and in seronegative humans. In addition, recombinant pox viruses are useful to express AID virus proteins in cells used for assaying CTL responses and to understand the intracellular processing of AIDS virus proteins. In the following studies we will: 1. employ recombinant vaccinia viruses to study mechanisms of SIV escape from CTL recognition 2. assess the immunogenicity of novel recombinant vaccinia virus HIV-1 env constructs 3. compare the immunogenicity of recombinant Wyeth stain and MVA constructs 4. evaluate the immunogenicity of adeno-associated virus-HIV-1 gp120 constructs 5. characterize the immunogenicity of attenuated recombinant pox viruses delivered with cytokines